The invention relates to a circulation structure for a turbo compressor. In addition, the invention relates to a turbo compressor as well as to an aircraft engine and a stationary gas turbine.
Circulation structures or recirculation structures for turbo compressors are known in the form of so-called casing treatments and hub treatments. The primary task of circulation structures called casing treatments and hub treatments is increasing the aerodynamically stable operating range of the compressor by optimizing the surge limit distance. An optimized surge limit distance makes higher compressor pressures possible and therefore a higher compressor load. The malfunctions responsible for a local flow separation and ultimately for pumping the compressor occur on the housing-side ends of the rotor blades of one or more compressor stages or on the hub-side radially inner ends of the guides blades, because the aerodynamic load in the compressor is the greatest in these regions. The flow in the region of the blade ends is stabilized by circulation structures. Stator-side circulation structures in the region of the housing-side ends of the rotor blades are called casing treatments, whereas rotor-side circulation structures in the region of the hub-side ends of the guides blades area called hub treatments.
Flow structures for a turbo compressor that are configured as casing treatments and hub treatments, which have annular chambers that can be traversed in the circumferential direction, are known from German Patent Document No. DE 103 30 084 A1. The annular chambers that can be traversed in the circumferential direction are arranged concentrically to an axis of the turbo compressor in the region of the free blade ends of a rotor blade ring or a guide blade ring, wherein the annular chambers radially border a main flow channel of the turbo compressor. Guide elements may be arranged within the annular chambers that can be traversed in the circumferential direction.
Starting herefrom, the objective of the present invention is creating a novel circulation structure for a turbo compressor.
According to the invention, several chambers that can be traversed in an axial direction are situated upstream of the or each annular chamber, when viewed from the main flow direction of the main flow channel.
The present invention proposes for the first time that several chambers that can be traversed in an axial direction be arranged upstream of the or each annular chambers that can be traversed in the circumferential direction, when viewed from the main flow direction of the main flow channel. The circulation structure according to the invention accordingly combines chambers that can be traversed in the axial direction, which do not have a circumferential connection, with at least one annular chamber, which can be traversed in the circumferential direction, wherein the or each annular chamber is situated downstream from the chamber that can be traversed in the axial direction that does not have a circumferential connection, when viewed in the main flow direction. This permits the formation of a gap vortex to be pulsatingly inhibited in terms of its development. A forming recirculation flow uses fluid that has heavy losses to influence the inflow of the rotor-side components, wherein the geometric properties of the chambers that can be traversed in the axial direction that do not have a circumferential connection generate a counter twist. Additional flow obstruction regions are shifted to the annular chambers with a circumferential connection.
Because of its simplicity, the circulation structure according to the invention guarantees very low losses. Loss-generating, three-dimensional flow phenomena may be inhibited effectively. Positive effects for the operational stability of the turbo compressor under partial load and full load with an overall positive change in the efficiency, particularly under full load, can be linked hereby. The simplicity of the circulation structure is connected with low manufacturing costs.
Preferred further developments of the invention are disclosed in the following description. Without being limited hereto, exemplary embodiments of the invention are described in greater detail on the basis of the drawings.